Flexible displays

ABSTRACT

A process for creating an electronically addressable display includes multiple printing operations, similar to a multi-color process in conventional screen printing. In some of the process steps, electrically non-active inks are printed onto areas of the receiving substrate, and in other steps, electrically active inks are printed onto different areas of the substrate. The printed display can be used in a variety of applications. This display can be used as an indicator by changing state of the display after a certain time has elapsed, or when a certain pressure, thermal, radiative, moisture, acoustic, inclination, pH, or other threshold is passed. In one embodiment, the display is incorporated into a battery indicator. A sticker display is described. The sticker is adhesive backed and may then be applied to a surface to create a functional information display unit. This invention also features a display that is both powered and controlled using radio frequencies. It describes a complete system for controlling, addressing, and powering a display. The system includes an antenna or antennae, passive charging circuitry, and active control system, a display, and an energy storage unit. There is also a separate transmitter that provides the remote power for the display. The system is meant to be used anywhere it is useful to provide intermittent updates of information such as in a store, on a highway, or in an airport. A tile-based display allowing a modular system for large area display is created using a printable display material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 08/504,896filed Jul. 20, 1995, U.S. Ser. No. 08/983,404 abandoned filed Mar. 20,1997, and U.S. Ser. No. 08/935,800 filed Sep. 23, 1997, the contents ofall of which are incorporated herein by reference. This applicationclaims priority to U.S. Ser. No. 60/057,133 filed Aug. 28, 1997, U.S.Ser. No. 60/057,716, filed Aug. 28, 1997, U.S. Ser. No. 60/057,122,filed Aug. 28, 1997, U.S. Ser. No. 60/057,798, filed Aug. 28, 1997, U.S.Ser. No. 60/057,799 filed Aug. 28, 1997, U.S. Ser. No. 60/057,163 filedAug. 28, 1997, U.S. Ser. No. 60/057,118, filed Aug. 28, 1997, U.S. Ser.No. 60/059,358, filed Sep. 19, 1997, U.S. Ser. No. 60/059,543 filedSept. 19, 1997, U.S. Ser. No. 60/065,629, filed Nov. 18, 1997, U.S. Ser.No. 60/065,630 filed Nov. 18, 1997, U.S. Ser. No. 60/065,605 filed Nov.18, 1997, U.S. Ser. No. 60/066,147, filed Nov. 19, 1997, U.S. Ser. No.60/066,245, filed Nov. 20, 1997, U.S. Ser. No. 60/066,246, filed Nov.20, 1997, U.S. Ser. No. 60/066,115 filed Nov. 21, 1997, U.S. Ser. No.60/066,334 filed Nov. 21, 1997, U.S. Ser. No. 60/066,418 filed Nov. 24,1997, U.S. Ser. No. 60/070,940 filed Jan. 9, 1998, U.S. Ser. No.60/071,371 filed Jan. 15, 1998, U.S. Ser. No. 60/072,390 filed Jan. 9,1998, U.S. Ser. No. 60/070,939 filed Jan. 9, 1998, U.S. Ser. No.60/070,935 filed Jan. 9, 1998, U.S. Ser. No. 60/074,454, filed Feb. 12,1998, U.S. Ser. No. 60/076,955 filed Mar. 5, 1998, U.S. Ser. No.60/076,959 filed Mar. 5, 1998, U.S. Ser. No. 60/076,957 filed Mar. 5,1998, U.S. Ser. No. 60/076,956 filed Mar. 5, 1998, U.S. Ser. No.60/076,978 filed Mar. 5, 1998, U.S. Ser. No. 60/078,363 filed Mar. 18,1998, U.S. Ser. No. 60/081,374 filed Apr. 10, 1998, U.S. Ser. No.60/081,362 filed Apr. 10, 1998, U.S. Ser. No. 60/083,252 filed Apr. 27,1998, U.S. Ser. No. 60/085,096 filed May 12, 1998, U.S. Ser. No.60/090,223 filed Jun. 22, 1998, U.S. Ser. No. 60/090,222 filed Jun. 22,1998, U.S. Ser. No. 60/090,232 filed Jun. 22, 1998, U.S. Ser. No.60/092,046 filed Jul. 8, 1998, U.S. Ser. No. 60/092,050 filed Jul. 8,1998, U.S. Ser. No. 60/092,742 filed Jul. 14, 1998, and U.S. Ser. No.60/093,689 filed Jul. 22, 1998, the contents of all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to display applications, and inparticular, to flexible displays.

BACKGROUND OF THE INVENTION

Many applications can benefit from inclusion of a display. For example,projection devices, sketching apparatuses, telephones, pocketbooks, andbattery indicators are only a few applications that display transientinformation. To date, widespread incorporation of displays has beenhindered because such applications generally require flexible displaysthat consume very little power.

Despite much effort directed to developing highly-flexible, reflectivedisplay media, there are relatively few examples of displays formed onsemi-flexible substrates, and these examples have found only moderatesuccess. For example, plastic-based liquid crystal displays, includingtwisted nematic (TN), supertwisted nematic (STN), polymer dispersedliquid crystal (PDLC), and bistable cholesteric liquid crystals havebeen developed. Nevertheless, problems remain with liquid crystalalignment in TN and STN displays, cholesteric displays are sensitive tochanges in their cell gap, and local stress can cause changes in thescattering or absorbance of PDLC and cholesteric films. As such, onlymoderate flexibility can be achieved with these displays.

Emissive electroluminescent films and organic light emitting diode filmscan be deposited on flexible substrates to create flexible displays.However, these devices require continuous power consumption foroperation, and thus are not practical for many applications.

Another problem with developing highly flexible displays is the lack ofan appropriate conductor for addressing the display elements. Typically,an indium tin oxide (ITO) layer vacuum sputtered onto a plasticsubstrate is used as a top conductor for displays. An ITO layer,however, can be damaged when the display is flexed. If the localcurvature of the plastic substrate becomes too great, the ITO layertends to crack, damaging the display.

SUMMARY OF THE INVENTION

An object of the invention is to provide a highly-flexible, reflectivedisplay which can be manufactured easily, consumes little (or no in thecase of bistable displays) power, and can, therefore, be incorporatedinto a variety of applications. The invention features a printabledisplay comprising an encapsulated electrophoretic display medium. Theresulting display is flexible. Since the display media can be printed,the display itself can be made inexpensively.

An encapsulated electrophoretic display can be constructed so that theoptical state of the display is stable for some length of time. When thedisplay has two states which are stable in this manner, the display issaid to be bistable. If more than two states of the display are stable,then the display can be said to be multistable. For the purpose of thisinvention, the term bistable will be used to indicate a display in whichany optical state remains fixed once the addressing voltage is removed.The definition of a bistable state depends on the application for thedisplay. A slowly-decaying optical state can be effectively bistable ifthe optical state is substantially unchanged over the required viewingtime. For example, in a display which is updated every few minutes, adisplay image which is stable for hours or days is effectively bistablefor that application. In this invention, the term bistable alsoindicates a display with an optical state sufficiently longlived as tobe effectively bistable for the application in mind. Alternatively, itis possible to construct encapsulated electrophoretic displays in whichthe image decays quickly once the addressing voltage to the display isremoved (i.e., the display is not bistable or multistable). As will bedescribed, in some applications it is advantageous to use anencapsulated electrophoretic display which is not bistable. Whether ornot an encapsulated electrophoretic display is bistable, and its degreeof bistability, can be controlled through appropriate chemicalmodification of the electrophoretic particles, the suspending fluid, thecapsule, and binder materials.

An encapsulated electrophoretic display may take many forms. The displaymay comprise capsules dispersed in a binder. The capsules may be of anysize or shape. The capsules may, for example, be spherical and may havediameters in the millimeter range or the micron range, but is preferablyfrom ten to a few hundred microns. The capsules may be formed by anencapsulation technique, as described below. Particles may beencapsulated in the capsules. The particles may be two or more differenttypes of particles. The particles may be colored, luminescent,light-absorbing or transparent, for example. The particles may includeneat pigments, dyed (laked) pigments or pigment/polymer composites, forexample. The display may further comprise a suspending fluid in whichthe particles are dispersed.

The successful construction of an encapsulated electrophoretic displayrequires the proper interaction of several different types of materialsand processes, such as a polymeric binder and, optionally, a capsulemembrane. These materials must be chemically compatible with theelectrophoretic particles and fluid, as well as with each other. Thecapsule materials may engage in useful surface interactions with theelectrophoretic particles, or may act as a chemical or physical boundarybetween the fluid and the binder.

In some cases, the encapsulation step of the process is not necessary,and the electrophoretic fluid may be directly dispersed or emulsifiedinto the binder (or a precursor to the binder materials) and aneffective “polymer-dispersed electrophoretic display” constructed. Insuch displays, voids created in the binder may be referred to ascapsules or microcapsules even though no capsule membrane is present.The binder dispersed electrophoretic display may be of the emulsion orphase separation type.

Throughout the specification, reference will be made to printing orprinted. As used throughout the specification, printing is intended toinclude all forms of printing and coating, including: premeteredcoatings such as patch die coating, slot or extrusion coating, slide orcascade coating, and curtain coating; roll coating such as knife overroll coating, forward and reverse roll coating; gravure coating; dipcoating; spray coating; meniscus coating; spin coating; brush coating;air knife coating; silk screen printing processes; electrostaticprinting processes; thermal printing processes; and other similartechniques. A “printed element” refers to an element formed using anyone of the above techniques.

In one aspect, the invention features an indicator. The indicatorincludes a substrate, a transducer, and an electrically addressabledisplay printed on the substrate in electrical communication with thetransducer. The transducer is, in some embodiments, printed on thesubstrate and, in other embodiments, is conventionally disposed on thesubstrate. The display shows a change in optical state in response to asignal from the transducer. In one embodiment, the indicator is abattery indicator. The battery indicator is in electrical communicationwith a battery and comprises an electrically addressable display printedon the battery. The optical state shows a first value in response to avoltage of the battery. In one detailed embodiment, the batteryindicator includes an electrophoretic display comprising amicroencapsulated display media, a first electrode and a secondelectrode disposed adjacent the electrophoretic display, a nonlinearelement, a voltage divider, and a resistor. The first and secondelectrodes apply an electric field to the electrophoretic display media.The nonlinear element is in electrical communication with a battery andthe first electrode. The nonlinear element conducts a battery voltage tothe first electrode when the battery voltage exceeds a predeterminedthreshold. The voltage divider is in electrical communication with thebattery and the second electrode. The voltage divider provides a voltageto the second electrode that is less than the battery voltage. Theresistor is in electrical communication with the nonlinear element andthe voltage divider.

In another aspect, the invention features a sticker display. Theelectrically active sticker display includes an encapsulated displaymedia and an adhesive layer disposed on the first surface of the displaymedia. In some cases, the encapsulated electrophoretic display may beitself sufficiently adhesive to function as a sticker without additionaladhesive layers. The display media comprises an optoelectrically activematerial. In one embodiment, a transparent layer including an electrodeis disposed adjacent a surface of the display media. In anotherembodiment, the sticker display further includes a via which extendsfrom the transparent layer to the adhesive layer.

In still another aspect, the invention features a method of printing anelectrically active display. The methods comprises the steps of: (a)providing a film having a clear electrode structure disposed on a firstsurface of the film; (b) printing a display media on the first surfaceof the film; and (c) printing or laminating a second electrode coveringat least a portion of the display media. The display media comprises anencapsulated optoelectrically active material dispersed in a binder

In still another aspect, the invention features a radio-controlleddisplay. The radio controlled display includes an electrically activedisplay having an encapsulated display media, a receiver, and a decoderin electrical communication with the receiver. The display is responsiveto the output of the decoder. In one embodiment, the display furtherincludes a power source in connection with the display. In anotherembodiment, the display further includes a plurality of row and columndrivers disposed on the substrate for addressing the display. In stillanother embodiment, the display further includes an antenna incommunication with a control circuit.

In still another aspect, the invention features a process for creatingan electrically addressable display. The method comprises the steps of(a) providing a substrate; and (b) printing an electrically active inkcomprising at least one microcapsule dispersed in a binder onto a firstarea of a receiving substrate. Optical qualities of the electricallyactive ink are modulated responsive to broadcast signals.

In still another aspect, the invention features a process for printingan electrically addressable display. The method comprises the steps of:(a) providing a substrate; and (b) printing an electrically active inkcomprising at least one microcapsule dispersed in a binder onto a firstarea of the receiving substrate.

In still another aspect, the invention features an electrically activedisplay tile. The tile includes a substrate, an electrically addressabledisplay disposed on the substrate, a controller disposed on thesubstrate in electrical communication with the display, and a connectordisposed on the substrate for connecting the display tile to anotherdisplay tile. The display comprises a encapsulated display medium. Inone embodiment, the display tile further includes a receiver forreceiving radio signals or other electromagnetic radiation, and thecontroller changes the display in response to the received radiosignals. In another embodiment, the display tile further includes amemory element storing data, and the controller changes the displayresponsive to data stored in the memory element.

In still another aspect the invention features a wearable display. Awearable display includes an article of clothing including anelectrically addressable display incorporated into the wearable item anda controller in electrical communication with the display. The displaycomprises an encapsulated display media. In one embodiment, thecontroller is incorporated into the wearable item. In anotherembodiment, the wearable item comprises a fashion accessory. In stillanother embodiment, the wearable item includes an interface forreceiving information from another device that can be displayed by thewearable item, such as a temperature monitor or position-sensing device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed with particularity in the appended claims. Theadvantages of the invention described above, together with furtheradvantages, may be better understood by referring to the followingdescription taken in conjunction with the accompanying drawings. In thedrawings, like reference characters generally refer to the same partsthroughout the different views. Also, the drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention.

FIG. 1 shows an exploded view of one embodiment of a printed flexibleelectrophoretic display.

FIG. 2 shows a block diagram of an indicator prepared according to thepresent invention.

FIG. 3 shows a circuit diagram of an embodiment of a battery indicator.

FIG. 3A shows a voltage-current curve of a non-linear element includedin a battery indicator.

FIGS. 4A-4B show various embodiments of display media that is notbistable.

FIGS. 5A-5F show various embodiments of a sticker display.

FIG. 6A shows a flow chart illustrating how one embodiment of aradio-controlled display functions.

FIG. 6B shows one embodiment of a radio-controlled display.

FIG. 7 shows one embodiment of a radio paper.

FIGS. 8A-8D depict a tile display system.

FIG. 8E shows one embodiment of a block diagram of a tile display.

FIG. 9 shows one embodiment of a wearable display.

FIG. 10 shows a block diagram of one embodiment of network datadisplays.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a substrate is provided and anelectronic ink is printed onto a first area of the substrate. Thepresent invention takes advantage of the physical properties of anelectronic ink which permits a wide range of printing and coatingtechniques to be used in creating a display. An electronic ink is anoptoelectronically active material which comprises at least two phases:an electrophoretic contrast media phase and a coating/binding phase. Theelectrophoretic phase comprises, in some embodiments, a single speciesof electrophoretic particles dispersed in a clear or dyed medium, ormore than one species of electrophoretic particles having distinctphysical and electrical characteristics dispersed in a clear or dyedmedium. The coating/binding phase includes, in one embodiment, a polymermatrix that surrounds the electrophoretic phase. In this embodiment, thepolymer in the polymeric binder is capable of being dried, crosslinked,or otherwise cured as in traditional inks, and therefore a printingprocess can be used to deposit the electronic ink onto a substrate. Anelectronic ink is capable of being printed by several differentprocesses, depending on the mechanical properties of the specific inkemployed. For example, the fragility or viscosity of a particular inkmay result in a different process selection. A very viscous ink wouldnot be well-suited to deposition by an inkjet printing process, while afragile ink might not be used in a knife over roll coating process.

The optical quality of an electronic ink is quite distinct from otherelectronic display materials. The most notable difference is that theelectronic ink provides a high degree of both reflectance and contrastbecause it is pigment based (as are ordinary printing inks). The lightscattered from the electronic ink comes from a very thin layer close tothe top of the viewing surface. In this respect it resembles a common,printed image. Thus, electronic ink is easily viewed from a wide rangeof viewing angles in the same manner as a printed page. Such inkapproximates a Lambertian contrast curve more closely than any otherelectronic display material. Since electronic ink can be printed, it canbe included on the same surface with any other printed material.Electronic ink can be made optically stable in all optical states, thatis, the ink can be set to a persistent optical state. Fabrication of adisplay by printing an electronic ink is particularly useful in lowpower applications because of this stability.

If desired, the colors of electronically active and non-active inks mayclosely match and the reflectivities may be similar. Electronic inks canbe printed so that no border is noticeable between active and non-activeinks. This is referred to as “color matching” or “color masking”.Therefore, a display comprising an electronically active portion mayappear as if it is not electronically active when the display is notbeing addressed and may be activated by addressing the display.Electronic inks are described in more detail in co-pending U.S. patentapplication Ser. No. 08/935,800, the contents of which are incorporatedherein by reference.

Referring to FIG. 1, a display 1 is created by printing a firstconductive coating 2 on a substrate 3, printing an electronic ink 4 onthe first conductive coating 2, and printing a second conductive coating6 on the electronic ink 4. Conductive coatings 2, 6 may be Indium TinOxide (ITO) or some other suitable conductive material. The conductivelayers 2, 6 may be applied from a vaporous phase, by electrolyticreaction, or deposition from a dispersed state such as spray droplets ordispersions in liquids. Conductive coatings 2, 6 do not need to be thesame conductive material. In one detailed embodiment, the substrate 3 isa polyester sheet having a thickness of about 4 mil, and the firstconductive coating 2 is a transparent conductive coating such as ITO ora transparent polyaniline. The second conductive coating 6 may be anopaque conductive coating, such as a patterned graphite layer.Alternatively, the second conductive coating 6 can be polymeric. Thepolymer can be intrinsically conductive or can be a polymer carrier witha metal conductor such as a silver-doped polyester or a silver-dopedvinyl resin. Conductive polymers suitable for use as the secondelectrode include, for example, polyaniline, polyprrole, polythiophene,polyphenylenevinylene, and their derivatives. These organic materialscan be colloidally dispersed or dissolved in a suitable solvent beforecoating.

In another embodiment shown in FIG. 1A a display 1 is created byprinting a first conductive coating 2, on a first substrate 3 (step 102)printing an electronic ink 4 on the first conductive coating 2 step(104) printing a second conductive coating 6 on a second substrate 3′(step 106) and configuring the substrates 3, 3′ such that the secondconductive coating 6 is in electrical communication with the electronicink 4 (step 108).

The electronic ink 4 comprises a plurality of capsules. The capsules,for example, may have an average diameter on the order of about 100microns. Capsules this small allow significant bending of the displaysubstrate without permanent deformation or rupture of the capsulesthemselves. The optical appearance of the encapsulated medium itself ismore or less unaffected by the curvature of these capsules.

One of the benefits of using printing methods to fabricate displays iseliminating the need for vacuum-sputtered ITO by using coatableconductive materials. The replacement of vacuum-sputtered ITO with aprinted conductive coating is beneficial in several ways. The printedconductor can be coated thinly, allowing for high optical transmissionand low first-surface reflection. For example, total transmission canrange from about 80% to about 95%. In addition, the printed conductivecoating is significantly less expensive than vacuum-sputtered ITO.Another advantage of the encapsulated electrophoretic-display medium isthat relatively poor conductors, for example, materials withresistivities on the order of 10³-10¹² ohms square, can be used as leadlines to address a display element.

The flexible, inexpensive display described above is useful in numerousapplications. For example, these, flexible displays can be used inapplications where paper is currently the display medium of choice.Alternatively, the displays can be made into disposable displays. Thedisplays can be tightly rolled or bent double. In other embodiments, thedisplays can be placed onto or incorporated into highly flexible plasticsubstrates, fabric, or paper. Since the displays can be rolled and bentwithout sustaining damage, they form large-area displays which arehighly portable. Since these displays can be printed on plastics theycan be lightweight. In addition, the printable, encapsulatedelectrophoretic display of the present invention can maintain the otherdesirable features of electrophoretic displays, including highreflectance, bistability, and low power consumption.

The printable display described above can be incorporated into a varietyof applications. In one embodiment, the invention features a new type ofindicator that can be printed in its entirety. FIG. 2 shows a blockdiagram of an indicator 10. The indicator 10 includes an electronicallyaddressable display 12 which is capable of changing between at least twostates, and a transducer 14 which is capable of generating an electricalevent to trigger the change in the state of the display 12. Theelectronically addressable display 12 and the transducer 14 can both beprinted onto a substrate 16. FIG. 2 depicts an embodiment in which theindicator 10 further includes a printed battery 18 to power thetransducer 14 and the display 12. In one embodiment, the transducer 14need not be printed. In this embodiment, a conventional transducer 14may be placed on the substrate 16. The display media 12 is printed asdescribed above. The media 12 may be printed before or after thetransducer adjacent which it is placed, provided that the display media12 is ultimately in electrical communication with the transducer 14.

In another embodiment, the battery 18 is a conventional battery, thevoltage of which is measured and displayed on the display 12. In onedetailed embodiment, a battery indicator includes a printed displaydirectly connected to a battery. The battery continuously addresses thedisplay, but as the battery discharges over time, it eventually reachesa point where it is incapable of addressing the display. By varying thecharacteristics of the transducer, for example the number of amp-hourscontained by the battery, the battery indicator can function as a“timer,” so that the display shows a message such as “expired” afterpassage of a certain electrical charge.

FIG. 3 shows a circuit diagram of a battery indicator 20. The batteryindicator 20 includes a display 22 comprising a display media 24, afirst electrode 26 and a second electrode 27 disposed adjacent thedisplay media 24, a nonlinear element 28 in electrical communicationwith the first electrode 26 and a battery 30, a voltage divider 32 inelectrical communication with the battery 30 and the second electrode27, and a resistor 34 in communication with the nonlinear element 28 andthe voltage divider 32.

The battery 30 can be of any type. The battery 30 initially has amaximum voltage. The voltage divider 32 establishes a voltage potentialthat is some fraction of the battery cell voltage at the secondelectrode 27. In the embodiment shown in FIG. 2, the voltage divider 32includes high impedance resistors 36 and 38. The voltage divider 32, forexample, can have two 5 megaohm resistors to apply a voltage potentialthat is equal to one-half of the battery cell voltage to the secondelectrode 27. Alternatively, the battery indicator can have a slidingvoltage divider. A sliding voltage divider may be provided as apotentiometer using a non-linear element to control the voltage appliedto the display 24.

The nonlinear element 28 conducts voltage equal to the battery cellvoltage to the first electrode 26 when the battery cell voltage exceedsthe predetermined threshold voltage. Examples of suitable non-linearelements include a transistor, Zener diode, varistor,metal-insulator-metal structure, organic semiconductors and devicesbased on materials like pentacene or regio-regular polythiophene, or anyother nonlinear devices known to those skilled in the art. FIG. 3A showsan exemplary current-voltage characteristic of a nonlinear element 28which can be used in the battery indicator 20. The threshold voltage isadjustable through manufacturing, and the threshold is selected to be avoltage at which the battery 30 is still useable. As long as the battery30 is above the threshold, the junction breaks down and the firstelectrode 26 is set at the battery cell voltage. A useful batteryindicator should have a very low leakage current (e.g., much less than 1microampere (μA)) and should allow at least about a hundred times asmuch current to flow when it is on than when it is off. The thresholdvoltage at which the state of the display changes depends on the batterywith which the indicator is designed to work. A threshold voltage ofabout 8 volts (V) is typical for a 9 V alkaline. For example at 9 V, thedevice should pass 1 μA, at 8 V the device should pass 100 nanoamperes(nA), and at 7 V the device should pass 10 nA.

The voltage from the battery 30 which passes through the nonlinearelement 28 and is applied to the first electrode 26, combined with thevoltage from the battery 30 which passes through the voltage divider 32and is applied to the second electrode 27, to provide an electric fieldacross the display media 24 sufficient to activate the display 22. Atleast one of the first and second electrodes 26, 27 comprises a clearconductive material to permit viewing of the display 22. Alternatively,both electrodes may be placed on one side of the display media 24,eliminating the need for a clear electrode. Once the battery voltage 30drops below the threshold, however, the potential at the first electrode26 is drained through the resistor 34. Draining of the potential at thefirst electrode 26 changes the electric field across the display media24 such that an electric field of opposite polarity is applied to thedisplay media 24 and the appearance of the display 22 changes.

The resistor 34, for example, can be a 10 megaohm resistor for a typical9 V battery. A typical 9 V battery has a 400 milliampere hour (mAh)rating. Over a 5 year period, there are 43,800 hours (5 years×365days/year×24 hours/day=43800 hours). Thus, the indicator 20 must drawless than 1 μ(400 mAh/43800 h) in order for the battery 30 to have asuitable shelf life. Ideally, the indicator 20 should draw less than 1μA. In order to achieve such a low current draw, the impedance of theindicator 20 must be in the order of 10 megaohms.

As noted above, a circuit permanently connected to a battery shouldconsume very little power. A number of display materials are suitablefor such an application. However, some of these display materials, suchas a liquid crystal display, require a more complex cell in theirmanufacture. In the present invention, encapsulated electrophoreticdisplays and encapsulated twisting ball displays are preferred as thedisplay media 24 because of their low power draw, printability, and goodcontrast. Encapsulated electrophoretic display media, for example,includes a mixture of electrophoretic particles and a dye, orelectrophoretic particles comprising multiple optical properties.

In one embodiment in which the battery indicator 20 operates by applyingan electric field of one polarity while the battery is good, and thenswitching to the opposite polarity when the battery goes bad. Thus, thedisplay media is not required to be bistable.

Referring to FIG. 4A, a display media 180 that is not bistable comprisesat least one capsule 185, each filled with electrophoretic particles 210and a fluid 220. Such media is useful in battery applications becausethe media will exhibit one contrast state when the display is addressedby the battery and a second contrast state when not addressed by thebattery, i.e., when the battery voltage level falls below the thresholdvoltage necessary to address the display. In the embodiment depicted inFIG. 4A, electrophoretic particles 210 have polymer chain branches 200which cause one particle 210 to repel another particle 210. In onedetailed embodiment, the fluid 220 is dyed to provide a color contrastwith the particles 210. When the display media is addressed, theparticles 210 migrate towards an electrode with an opposite charge,thereby displaying the color of the particles 210. Once the displaymedia is no longer being addressed, the particles 210 repel each otherand redistribute within the fluid 220, thereby displaying the color ofthe fluid 220. This encapsulated display media 180 can be printed onto asubstrate to form a display. Alternatively, an electrophoretic displaythat is not bistable can be formed by providing a standard display cellfilled with electrophoretic media that is not bistable.

Referring to FIG. 4B, another display media 290 that is also notbistable includes at least one microcapsule or cell 292, filled with aplurality of metal sol 296 and a clear fluid 294. Metal sol 296comprises particles which are smaller than a wavelength of light. In onedetailed embodiment, the metal sol 296 comprises gold sol. When anelectric field is applied across the microcapsule or cell 292, solparticles 296 agglomerate and scatter light. When the applied electricfield is reduced to below a certain level, Brownian motion causes thesol particles 296 to redistribute, and the display media 290 appearsclear from the clear fluid 294.

In another detailed embodiment, multiple indicators mapped to differentvoltage thresholds are used to create a battery indicator. An importantelement in this embodiment is a circuit element that provides a sharpnon-linearity at a well-controlled voltage level.

In still another detailed embodiment, the battery indicator combinesmultiple non-linearities in order to provide a proper fit of the voltagecurve for the open circuit voltage to be mapped to the closed circuitvoltage. It is known that a battery with no load shows a voltage that isnot the same as the loaded voltage. Therefore, non-linearity may be usedto compensate for this difference. In addition, a known mapping of theclosed circuit voltage to open circuit voltage may be used in theprinted scale of the indicator.

In another detailed embodiment, the invention features a timer. A timerincludes ajunction formed of p-type semiconductor (e.g., boron doped)and an intrinsic or undoped semiconductor. In this device, current doesnot flow. However, if the intrinsic semiconductor becomes n-doped (i.e.,if the semiconductor has extra electrons available from the valenceshell of dopant atoms), then current could flow from the n-doped regionto the p-doped region. Normally, intrinsic semiconductors become n-dopedif doped with phosphorous. Alternatively, the same result can beachieved by embedding or placing in close proximity to the intrinsicregion a beta particle emitting substance such as tritium. Likewise, theintrinsic region of an n-doped-intrinsic junction semiconductor may betreated with an alpha particle emitter such as Helium-5 to convert it toa p-doped region. Over time, a non-conducting junction with an alpha orbeta particle emitter embedded in its intrinsic region transforms into adiode-type junction which passes current, thereby acting as a timer.

In another detailed embodiment, a timer employs a p-n junctionsemiconductor sensitive to light, such that light forces a current toflow from the n-region to the p-region. The timer can include atritiated phosphor in a Zener diode and a display. A Zener diode is adiode designed to survive reverse breakdown. Light applied to the Zenerdiode through the tritiated phosphor increases the breakdown voltage ofthe Zener diode. When the tritiated system wears out, the Zener diodebreakdown voltage decreases and voltage is applied to the display.

In another detailed embodiment, a pressure indicator includes atransducer and a display. In some embodiments, the transducer isprinted. In other embodiments, the display is an encapsulatedelectrophoretic display. The transducer, for example, comprises aprinted mechanical switch which closes once a certain pressure thresholdis exceeded, thereby causing a printed display to change its state. Inanother example, pressure can change the electrical characteristics(e.g., the capacitance) of a circuit containing the display, therebychanging the state of the display once a threshold value has beenexceeded. Alternatively, the transducer can provide power to switch thestate of the display. One example of such a transducer is apiezoelectric element. In other embodiments, a solar cell may providepower to the display.

In another detailed embodiment, a heat indicator includes a display anda thermally-sensitive structure capable of changing the state of thedisplay in response to a thermal stimulus. In some embodiments thestructure is printed. In other embodiments the display is anencapsulated electrophoretic display. For example, a printed bimetallicmechanical system can serve as an electrical switch which changes thestate of the printed display. Alternatively, a printed chemicalstructure which reacts to a thermal condition can be used to change theresulting electrical properties and the state of the display. Stillanother possibility is a transducer which provides power to switch thestate of the display, for example, from an electrochemical potential. Inother embodiments, a solar cell may provide power to the display.

In another detailed embodiment, a light indicator includes a display anda photosensitive structure capable of changing the state of the displayin response to a photonic stimulus. In some embodiments the structure isprinted. In other embodiments the display is an encapsulatedelectrophoretic display. For example, a printed solar cell array has aphotovoltaic characteristic which is capable of providing a voltage toswitch the state of the display in response to incident photons. Otherstructures which are sensitive to other radiative ranges (e.g. infrared,ultraviolet, etc.) could also be printed onto a substrate with thedisplay. In other embodiments, a solar cell may provide power to thedisplay.

In another detailed embodiment, a moisture indicator includes a displayand a moisture-sensitive structure capable of changing the state of thedisplay in response to humidity or direct aqueous contact. In someembodiments the structure is printed. In other embodiments the displayis an encapsulated electrophoretic display. For example, a structure canbe printed which is an open circuit until an ionic solution bridges twoexposed electrical contacts, thus changing the state of the display.Alternatively, a chemical structure can be printed which, after theabsorption of a certain amount of water, changes the electricalproperties sufficiently to change the state of the display. Thistransducer can provide power to switch the state of the display, forexample using an accumulated electrochemical potential. Useful materialsfor this purpose include polyvinylalcohol, poly-N-vinylpyrrolidone,polyvinylpyrrolidone, derivatives of these materials, starches, andsugars. In other embodiments, a solar cell may provide power to thedisplay.

In still another detailed embodiment, a sound indicator includes adisplay and an acoustically-sensitive structure capable of changing thestate of the display in response to an acoustical stimulus. In someembodiments the structure is printed. In other embodiments the displayis an encapsulated electrophoretic display. For example, a mechanicallyresonating structure could be printed which changes the state of thedisplay based on piezoelectrically generated energy, similar to amicrophone. In other embodiments, a solar cell may provide power to thedisplay.

In still another detailed embodiment, an angle indicator includes adisplay and a structure sensitive to orientation that is capable ofchanging the state of the display in response to a change in theorientation of the indicator. In some embodiments the structure isprinted. In other embodiments the display is an encapsulatedelectrophoretic display. For example, a mercury switch type structurecould be provided which closes two electrical contacts when a certainorientation has been reached. The orientation structure can also providepower to switch the state of the display. For example, the transducercan include a mechanical structure which converts a mechanical energyinvolved in angular rotation into an electrical energy. In otherembodiments, a solar cell may provide power to the display.

In still another detailed embodiment, a pH indicator includes a displayand a pH-sensitive structure capable of changing the state of thedisplay in response to a change in the pH of a solution in which theindicator is immersed. In some embodiments the structure is printed. Inother embodiments the display is an encapsulated electrophoreticdisplay. For example, a chemical cell which undergoes a chemicalreaction at a certain pH level can be printed and can change the stateof the display. The pH-sensitive structure can also provide power toswitch the state of the display. For example, an electrochemicalpotential can be generated by the chemical reaction. In otherembodiments, a solar cell may provide power to the display.

In still another detailed embodiment, a chemical indicator includes adisplay and a chemically-sensitive structure capable of changing thestate of the display in response to an external chemical interference.In some embodiments the structure is printed. In other embodiments thedisplay is an encapsulated electrophoretic display. For example, aprinted chemical sensor can be sensitive to an externally introducedagent which causes a chemical reaction to occur, and switches the stateof the display. The chemically-sensitive structure can also providepower to switch the state of the display. For example, anelectrochemical potential can be generated by the chemical reaction. Inother embodiments, a solar cell may provide power to the display.

Additional transducers, other than those described above, that arecapable of providing a signal to change the state of the display inaddition to providing power to change the state of the display will bereadily apparent to those of ordinary skill in the art.

In still another detailed embodiment, any of the above transducers canbe connected to another transducer to create a multi-level transducerpath which changes the state of display. For example, an indicator caninclude a chemically-sensitive structure, a thermally-sensitivestructure, and a display, all of which may be printed on a substrate.Heat from an exothermic reaction created by the chemically-sensitivestructure can be sensed by the thermally-sensitive structure, which inturn changes the state of the display and may also be used to power thedisplay.

In another embodiment, an encapsulated electrophoretic display is usedto create a printable, adhesive display. Referring to FIG. 5A, aprintable, adhesive display 40 includes a substrate 42 coated with aconducting layer forming a top electrode 44, a display media 46 disposedadjacent the top conductor 44, and an adhesive 48 disposed adjacent thedisplay media 40. The display media 40 comprises an optoelectricallyactive component 50 and a binder 52 which holds the optoelectricallyactive component 50 together. The substrate 42 and the top electrode 44are optically transmissive to allow the display 40 to be viewed throughthe electrode. The substrate 42, for example, can be formed of apolymeric material such as a polyester. The top electrode 44, forexample, can be formed of an inorganic material such as ITO or asuitable polymeric material. The optoelectronically active component 50,for example, can be an encapsulated electrophoretic display material.Alternatively, the optoelectronically active component 50 can be anyother suitable display material such as bichronnal microspheres orliquid crystals. The binder 52, for example, can be selected frompolyurethanes, polyvinylalcohols, gelatins, polyacrylates, polystyrenes,polyvinylbutyrals, polyesters, epoxies, silicones, polycarbonates, theirderivatives, and pressure-sensitive urethanes and adhesives.

In operation, the adhesive display 40 is attached to a receiving surface(not shown) by the adhesive 48. The receiving surface may include rearelectrodes for addressing the optoelectronically active component 50.The rear electrodes may be electrically connected to drive or powercircuitry for operating the display 40. In this embodiment, the display40 is addressed in a “coupling” mode, where the top electrode 42 is“floating” and not directly tied to any specific potential.

Referring to FIG. 5B, an adhesive display 56 includes a substrate 42, atop electrode 44 disposed on the substrate 42, a display media 46comprising an optoelectronically active component 50 and a binder 52,the display media 46 disposed adjacent the top electrode 44, and anadhesive 48 disposed adjacent display the media 46. In this embodiment,the adhesive display 56 further includes a via 60 which electricallyconnects the top electrode 44 to a pad 62 disposed on a rear surface ofthe display media 46, and a conductive adhesive 64 is disposed adjacentthe pad 62. The rear electrodes are disposed on a receiving surface (notshown) to which the adhesive display 56 is applied. In this embodiment,the top electrode 44 may be directly connected to a specific potential.

Referring to FIG. 5C, an adhesive display 70 includes a substrate 42, apatterned, optically-transmissive conducting layer 72 forming aplurality of top electrodes, the layer 72 being on the substrate 42, adisplay media 46 comprising an optoelectronically active component 50and a binder 52 disposed adjacent the substrate 42, and an adhesive 48disposed adjacent the display media 46. The adhesive display 70 furtherincludes at least one via 60 which electrically connects at least onetop electrode 72 to a pad 62 disposed on a rear surface of the displaymedia 46. A conductive adhesive 64 may be disposed adjacent the displaymedia in the general location of the pads 62. The rear electrodes may bedisposed on a receiving surface (not shown) to which the adhesivedisplay 70 is applied.

Referring to FIG. 5D, an adhesive display 80 includes a substrate 42, acontinuous top electrode 44 disposed on the substrate 42, a displaymedia 46 comprising an optoelectronically active component 50 and abinder 52 disposed adjacent the top electrode 44, at least one patternedrear electrode 82 disposed adjacent a rear surface of the display media46, and conductive adhesive 64 disposed adjacent the rear electrodes 82for adhering the display 80 to a receiving surface (not shown). In thisembodiment, the receiving surface may include drive or power circuitryfor operating the display 80. In this embodiment, the display 80 isaddressed in a “coupling” mode where the top electrode is “floating.”

Referring to FIG. 5E, an adhesive display 90 includes a substrate 42, atleast one patterned top electrode 72 disposed on the substrate 42, adisplay media 46 comprising an optoelectronically active component 50and a binder 52 disposed adjacent the top electrode 72, at least onepatterned rear electrode 82 disposed adjacent a rear surface of thedisplay media 46, and a dielectric layer 92 disposed adjacent the rearelectrodes 82. The adhesive display 90 further includes at least one via60 which extends from a top electrode 72 through the display media 46and the dielectric layer 92 to at least one pad 62 disposed on a rearsurface of the dielectric layer 92. The adhesive display 90 furtherincludes at least one via 94 which extends from a rear electrode 82through the dielectric layer 92 to at least one pad 96 disposed on arear surface of the dielectric layer 92. Conductive adhesive 64 isdisposed in the general location of the pads 62 and 96 to adhere thedisplay 90 to a receiving surface and to provide electricalcommunication between circuitry on the receiving surface and theelectrodes 72, 82 of the display 90. The display 90 can further includea nonconductive adhesive 48 disposed adjacent the exposed dielectriclayer 92 to fturther assist in adhering the display 90 to the receiver.

Referring to FIG. 5F, an adhesive display 98 includes a substrate 42, adisplay media 46 comprising an optoelectronically active component 50and a binder 52 disposed adjacent the substrate 42, and an adhesive 48disposed adjacent a rear surface of the display media 46. In thisembodiment, the display 98 is addressed by rear electrodes (not shown)only. The rear electrodes are disposed on a receiving surface to whichthe display 98 is applied. Alternatively, the rear electrodes may bedisposed on a rear surface of the display 98 as shown in FIGS. 5D and5E.

In the embodiments described above, a stylus may be provided that actsas the top electrode to address the adhesive display 40. In thisembodiment, the stylus may be scanned over the entire display to addressit. Alternatively, the stylus may be used as a writing utensil,addressing only specific portions of the display over which it ispassed.

In another embodiment, an encapsulated, electrophoretic display is usedto form a radio-controlled display system. Referring to FIG. 6A, theradio-controlled display system 300 includes a remote transmitter 370, areceiver 301, a controller 340, and a display unit 350. In oneembodiment, the receiver 301 includes an antenna 302. In one moreparticular embodiment, the receiver 301 is in electrical communicationwith a passive rectifier 310 which transforms and rectifies energyreceived by the antenna 302. The antenna 302 can be a monopole antenna,a dipole antenna, a planar array, a coil or any other antenna structureknown in the art of radio reception.

As shown in FIG. 6B, the antenna 302 may be disposed in a surroundingrelation to the display 350, allowing power to be received fromrelatively low-power signals. For example, an antenna having across-sectional area of 0.1 square meters that receives a 10,000 wattsignal at a distance of 5,000 m can receive 3 microwatts of power. Inother embodiments the display 350 is powered by a solar cell (notshown).

In one embodiment, the antenna 302 includes a plurality of antennas toimprove the reception level. The display system 300 further includes anenergy storage device 320 in communication with the passive rectifier310. The energy storage device 320 can be a capacitor, a battery, or anyother electrical or non-electrical energy storage device known in theart of energy storage. In the case of a non-electrical energy storage, atransducer can be used to transfer electrical energy into another formof energy.

When the energy level in the energy storage device 320 reaches a certainlevel as detected by an energy level detector 330, the controller 340 isactivated and the display can be updated. The controller 340 decodes theradio signals received by the antenna 302 and updates the display 350based on the information received by the antenna 302. Each display 350can have a unique identification code 360 that may be stored as dipswitch settings or as programmed data in a semiconductor device such asa PROM or Flash RAM as in cellular phones or beepers. The controller 340looks for this identification number 360 and updates the display 350with the information on the attached data stream if a match between thetransmitted ID code and the stored identification number 360 is made.

In a preferred embodiment, the display 350 is a low power display. Forexample, a bistable, non-emissive display, such as an electrophoreticdisplay can be used. In one detailed embodiment, an encapsulated,electrophoretic display, which is inexpensive and easy to manufactureinto a finished product, can be used.

In one detailed embodiment, the radio-controlled display forms a radiosign that can be updated using information sent via radio-frequencyenergy. The sign includes a surface covered with a display material andcontrol circuitry. This control circuitry receives broadcast energy. Thecircuitry decodes the information and updates the sign with thatinformation.

The display material, for example, can be an encapsulated,electrophoretic display or any other encapsulated display material knownto those skilled in the art. These display materials can be printedusing traditional printing technology, thus facilitating and loweringthe cost of sign manufacture. Radio signs can be used in stores,airports, train stations, on roads, supermarkets, at conventions, asbillboards, or as any other signs where updating the signs or poweringthe signs may be best done remotely. Content may be updated using anyform of electromagnetic radiation. These signs can use solar cells,batteries, or a hardwired source of power. These signs may be in twocolors, three colors, four colors, or full color.

A color display may be fabricated with a multi-step printing process.For example, the first four steps can be a traditional four-color screenprinting process to lay down an elaborate border or various staticinformation that will not change throughout the lifetime of the device.The next step can be printing an electronic ink, which may be selectedto match exactly the resultant colors from the four-color process. Insome embodiments, a top electrode is disposed on the printed electronicink. The top electrode may also be printed using conventional printingtechniques.

In one detailed embodiment, the electronic ink comprises encapsulatedelectrophoretic ink which includes TiO₂ particles mixed into an organicfluid. The organic fluid, for example, may contain a colored dye. Theorganic dispersion is emulsified into an aqueous solution andencapsulated using any of known encapsulation procedures known to thoseskilled in the art. Examples of such materials include gelatin-gumarabic or urea-formaldehyde microcapsules. In this embodiment, thecapsules are blended with a binding material to form a printableelectronic ink suspension.

In another embodiment, a color display may be fabricated using alamination process. In this embodiment, static information is printed ona first substrate. In this embodiment, the first embodiment includes atleast one clear, or substantially clear, aperture. An encapsulatedelectrophoretic display is laminated to the printed substrate so thatthe display aligns with the aperture.

In another detailed embodiment, a radio-controlled display forms adevice capable of receiving broadcast data for individual consumption,referred to herein as a radio paper. The content may be customized foran individual, and a consumer of information could pay for suchcustomized content using an electronic payment scheme. Radio paper maybe two-color (e.g. black and white) or full color, as described above.Transactions for content may take place over one or more computernetworks, including the world-wide computer network known as theInternet. Referring to FIG. 7, a radio paper 400 includes a substrate402, a display 404 disposed on the substrate 402, a receiver 406disposed on the substrate 402, and control circuitry 408 disposed on thesubstrate 402. The display 404 can be printed onto the substrate 402.Alternatively, flip chip technology can be used to mount a siliconsubstrate 402 to a display substrate 404. The control circuitry 408 canbe created directly on the substrate 402 using low temperaturepoly-silicon process. A plurality of row and column drivers can beinterfaced to the backplane of the display 404 for addressing thedisplay 404. In one detailed embodiment, the radio receiver 406 includestraces disposed on the substrate 402. In another detailed embodiment,the radio receiver 406 includes an antenna mounted on the substrate 402.The radio paper 400 can further include a power source 410 disposed onthe substrate 402. The power source 410, for example, can be a solarcell, a thin film battery, or a standard cell.

The radio paper described above can be used to provide a wirelessupdatable document. The device includes: a document cover; an electronicdisplay on any surface of the cover; and a data receiver. The display isfed by data from the data receiver. The display is visible to thedocument user and represents a way for the document to be messagedsubsequent to its delivery. The device can be provided as a leaflet,book, magazine, circular, periodical, catalogue, directory or itemcontaining a document cover. Ideally the electronic display of thedevice should operate using very low power and be easily visible. Thegeneral class of reflective electronic displays is desirable for thisreason. Further ideally the display would be bistable, as describedabove, in order to minimize power draw. In addition, ideally the displaywould be flexible and paper-thin to maximize the number of ways in whichthe display could be incorporated. For example, a paper-thin substratewould allow the radio paper to be addressed by a desktop unit such as alaser printer. Alternatively, the radio paper could be addressed using astylus that can be passed over the display. An encapsulatedelectrophoretic display meets all of the stated requirements, and may beused beneficially for this purpose.

The data receiver may be any device capable of receiving information viaelectromagnetic radiation. In some particular embodiments, the datareceiver is a pager or other radio receiver. In other embodiments thedata receiver may receive data via a physical connection, such ascoaxial cable.

The device may operate by battery power. In this case, the device mayincorporate an appropriate sleep mechanism that causes the receiver toonly be powered for reception during certain moments of the day whenmessages are expected to be sent, such as low traffic periods wherebandwidth is cheaper. The device may also incorporate a solar cell toeliminate or reduce the need for batteries.

An example of the usefulness of this device can be shown by reference toa chain of retail stores that distributes the device as a catalogue.After shipping the catalogue, the retailer may determine certaininventory items must be liquidated. This typically requires costlymarketing efforts. Instead, using the device, the chain may advertisethe items to be liquidated and may in fact refer the customer tospecific pages of the catalogue. The chain may also promote events atthe retail store and drive traffic to the store. The chain may also runvarious messages to different customer segments to evaluate offers andmarketing messages on a trial basis.

Ideally the device may be addressed either individually or as part of agroup of devices. In the former case this permits targeted marketing andin the latter case this saves on bandwidth transmission costs.

In still another embodiment, an encapsulated electrophoretic display isused to form a tile display, which allows creation of a large areadisplay by interconnecting a plurality of tile displays. The tiledisplays, when assembled, may or may not be seamless. Tile pixels mayhave any shape such as circular, rectangular or other shapes, forexample, shapes present in a mosaic font display. There may be a pixelmask applied in front of the pixels.

Referring to FIGS. 8A-8D, a tile display system 800 includes a pluralityof tile displays 801, 802, 803 and 804 and a controller (not shown).Each tile display 801 includes means for connecting the tile display 801to an adjacent tile display 802, 803, 804. The tile display system 800may include any desired number of tile displays. In one embodiment, thetile display system includes 40×30 grid of 16×16 pixel tiles to form aVGA resolution screen.

In one detailed embodiment, the tile display system comprises a directconnect structure, that is, each pixel has its own lead line from thecontroller. Each lead line may be a discrete or packaged transistorline. In this embodiment, a front surface of the substrate comprises ofa grid of electrodes, where each electrode is connected through a via tothe output of a control chip. Thus, for an N×N grid, N²+1 control linesare needed. The additional line is used to connect to a continuous topelectrode.

A matrix display using 2N+1 control lines can be built with a pluralityof tile displays using a variety of techniques. In one embodiment, anarray of varistors, metal-insulator-metal, or discrete diodes are usedfor individually addressing each pixel. In the case of diodes, discrete,surface-mount zener diodes are useful. For an N×N grid matrix display,using a matrix of two terminal devices, only 2*N+1 control lines areneeded to control the tiles.

In one detailed embodiment, the tiles are connected to each other usingstandard electronics connectors 805 placed on the edges of the tiles 801as shown in FIGS. 8A-8D. In another detailed embodiment, the tiles areconnected to each other using cables. The tiles can be mounted to awall, lightweight metal grid, or any other substrate using nuts solderedonto the back of the tiles or by any other means known in the art offastening substrates.

The controller includes a microprocessor or other suitable drivecircuitry. The controller transmits information to the tile displays toupdate the displays using any convenient form of electromagneticradiation. In some embodiments the controller also receives informationfrom the tile displays. Data for the display system may be stored in amemory element of the controller or may be received in the form ofelectromagnetic signals using a receiver. The receiver, for example, caninclude an antenna and a passive rectifier in communication with theantenna, as described above.

In one embodiment, the controller connects to a single tile and controlsthe entire display. The controller can consist of a battery, a powersupply, a paging receiver, and a microprocessor to control the entiresystem. The display can be powered, for example, using commerciallyavailable integrated AC to DC converters. In one embodiment, each tilemay have its own high voltage supply. Common inverter chips for use inelectroluminescent backlights can be used in this embodiment.

One method of controlling the entire tile system is to have amicrocontroller on each tile. In this embodiment, the sign controllertells the one tile it is connected to that it is at a certain coordinatelocation, say 0,0. Due to the asymmetrical connector layout, the tilecan determine to which edge the controller is connected. That tile thencommunicates with its neighbors, incrementing or decrementing thecoordinate location appropriately. Through this protocol, each tile candetermine a unique identification code that specifies its location onthe sign. The sign controller can then send data out on a common bus andeach tile's microcontroller can receive data needed to update the tile.When the appropriate data appears on the bus, the microcontroller shiftsthis data out to the display drivers. Then, the entire sign is given awrite pulse and the entire display is updated. The tile display asdescribed above may be successfully driven with a voltage as low as 3volts.

In one embodiment, the tile display is driven by controlling each pixeland the top electrode. To display an image, the electrodes of thebackplane are set to the proper pattern of voltages. The rear electrodesegments are set at either ground or power and the top electrode isswitched rapidly between ground and power. In the state where the topelectrode is at power, the areas of the display that have a potential ofground will be addressed and there will no field elsewhere. When the topelectrode is switched to ground, the other areas of the backplane thatare at power will be switched. This method allows the backplane tomaximize the voltage that the display material will receive.Alternatively, a standard bipolar addressing scheme may be used on therear electrodes, with the top electrode held at ground potential.

In one embodiment, high voltage CMOS display drive circuitry, such asHV57708PG manufactured by Supertex Corporation (Sunnyvale, Calif.) canbe used to drive the tile display. The HV57708PG is an 80 pin plasticgull wing surface mount chip that has 64 outputs. Each output can sink15 mA. Four of these chips can control a single tile. Other chips mayfind utility in the context of the present invention, such as the SharpLH1538 which is an 80V 128 line Tape-Automated-Bonding (TAB) chip.

Referring to FIG. 8E, a tile display 830 includes a substrate 831, and adisplay media 832, electronics 834, and driver circuitry 836. The tiledisplay 830 may be of any convenient size and may have any desirednumber of pixels. In one embodiment, the tile display 830 is 8 inches by8 inches, and is a matrix of 16×16 pixels. The substrate 831 of the tiledisplay 830 can be: a standard, etched printed circuit board; copperclad polyimide; polyester with printed conductive ink; or any othersuitable substrate with patterned conductive areas. A display media 832such as an encapsulated electrophoretic display media can be printed ona front surface of the substrate. The display media 832 can be anencapsulated electrophoretic suspension consisting of a slurry ofcapsules in a binder. Each capsule includes a mechanical systemconsisting of a dielectric suspending fluid and many particles. When anelectric field is applied across the capsule, the particles are causedto move in the field. By using two different particle species ofdifferent charge and color such as black and white, the viewer can bepresented with a color change. In one embodiment, the material isbistable, so that once it is addressed, it stays in its last state. Thisis used to eliminate power draw between image updates. The materialresponds purely to the field, thus the only real current draw is inchanging the charge of the plates on either side of the material. Thecapacitance of the display material can be between 0.1 and 100picofarads per square centimeter. The capacitance will vary withdifferences in the display material, binder, and overall thickness.

In one detailed embodiment, the display media is printed on a substrateand then covered with a layer of plastic or glass with a clearconductive coating such as ITO-coated, Mylar (Registered Trademark).Necessary connections to the ITO can be made using conductive adhesives,contacts, or tapes.

In the embodiment shown in FIG. 8E, the tile display 830 is preparedusing the following steps. An electronic ink which forms the displaymedia 832 is coated onto a conductive side of a sheet of ITO-sputteredMylar 835 and then dried or cured. A layer of conductive adhesive 836 isoptionally applied to the cured electronic ink 832 forming a laminate.This laminate is adhered to a backplane 837 made of a circuit boardhaving copper pads 838 or screen-printed metallic inks disposed on itssurface. The corners, or one edge 839 of the tile display 830, arereserved to allow connections to be made between the front ITO electrode833 and the backplane 837. If necessary, the electronic ink 832 isremoved from the corners 839 and a connection is made using a conductiveadhesive 836 such as silver loaded epoxy or a conductive heat seal.

In still another embodiment, encapsulated electrophoretic displays areincorporated into clothing to provide a wearable display. Referring toFIG. 9, a wearable display 502 is embodied as a patch on the arm 504 ofa jacket 500 providing weather maps 506 or other information. Thewearable display 502 includes a controller 508 in electricalcommunication with a display monitor 510 comprising an encapsulated,electrophoretic display media and a backplane. The display media isprinted onto the backplane. The backplane further includes electronicsnecessary for addressing the display 502. In some embodiments, thewearable display is in communication with at least one device thatprovides data for display, such as a global positioning unit, news feed,or a pager. In these embodiments, the data device communicatesinformation to the display which then displays the information for thewearer.

Wearable displays can be incorporated into other wearable items such asshoes, socks, pants, underwear, wallets, key chains, shoe laces,suspenders, ties, bow ties, buttons, buckles, shirts, jackets, skirts,dresses, ear muffs, hats, glasses, contact lenses, watches, cuff links,wallet chains, belts, backpacks, briefcases, pocket books, gloves,raincoats, watchbands, bracelets, overcoats, windbreakers, vests,ponchos, waistcoats, or any other article of clothing or fashionaccessory.

In still another aspect, the invention features a communications system.The communications system enables a whole new messaging andcommunication medium that permits its users to display messages in realtime in practically any location.

Referring to FIG. 10, the system 1000 comprises a plurality of displayreceivers 1002. The display receivers 1002 include an electronic display1004 and a data receiver 1006. In certain embodiments, the displayreceivers are tile displays or radio papers, as described above. Theelectronic display 1004 can operate by principles known to the art ofLCDs, plasma displays, CRTs, electrophoretic displays or encapsulatedelectrophoretic displays. The encapsulated electrophoretic display maybe coated onto many different surfaces practically any surface usingappropriate binders such as PVCs, urethanes and silicon binders,allowing them to be: made in large sizes (such as poster and billboardsizes) using coating techniques; lightweight enough to install withoutan overhead crane; flexible enough to bend with wind; and capable ofholding an image without further power draw, thereby operatingeconomically from solar cells or batteries.

The data receiver 1006 may be, for example, a pager, cellular phone,satellite phone, radio-frequency receiver, infrared receiver, cablemodem, or any other suitable receiver that is able to receiveinformation from another source. The data receiver 1006 can transmit aswell as receive information; for example the data receiver 1006 maytransmit verification information to confirm that a new data stream wasreceived. The data receiver 1006 may transmit data as may be useful forthe overall operation of the system 1000, for example weather data aspart of a national weather system. The data receiver 1006 may usevarying or multiple transmission methods for both receiving andtransmitting data.

The function of the data receiver 1006 is primarily to receive data andto display text or images in response. The data can include a message, astream of messages, codes describing how the device should display ortransition between the messages, or any other suitable information thatwill cause the display 1004 to operate as desired by the user. The datacan also include a header, error-checking, checksum, routing or otherinformation that facilitates the function of the system 1000.

In one embodiment, the data receiver 1006 includes a control system1008. The control system 1008 facilitates the operation of thecommunications system 1000. In one embodiment, the control system 1008functions as a user interface that permits the user to design, author,test, collaborate, approve and/or transmit images and commands that aresent to the display receivers. In another embodiment, the control system1008 functions as a billing and authorization system that monitors theuser's activity, verifies payment has been received, verifies that theaccount is in good standing, verifies that the user has properauthorization, creates usage reports, generates invoices, and/or updatesdata receivers due to unsatisfactory billing status. In anotherembodiment, the control system 1008 functions as a data receivermanagement system that tracks data receivers, generates reports of datareceiver history and status, permits sorting and screening of datareceivers based on suitable characteristics, and/or permits the user toassign messages to the entire network of data receivers or subsetsthereof. In still another embodiment, the control system 1008 functionsas a data transmission system that pre-processes data into a formatsuitable for the data receivers or subsets thereof, transmits the databy the method necessary or most suitable for each data receiver,schedules the transmission of the data according to desired criteria,verifies that the data was properly sent, receives and processes anyinformation uploaded from the data receivers 1006, resends messages thatmay not have been received, generates reports of such activities, and/orgenerates messages to field personnel indicating potential servicerequirements.

In all of the above embodiments, the control system may utilize theInternet or the World Wide Web as a user interface, as a datatransmission mechanism, as an error-checking protocol, as a messagingservice, as a programming environment or in any suitable fashion. Thecontrol system 1008 may also utilize data encryption mechanisms forenhanced security in the user interaction, in the system operation, inthe data receiver transmission or in the data receiver reception. Thecontrol system 1008 may also utilize a suitable digital payment schemeto enable funds to be transferred as a part of the overall system ofusage and operation.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A method of printing a flexible, electricallyactive display comprising the steps of: (a) providing a film having aclear electrode structure disposed on a first surface of the film; (b)printing a display media on the first surface of the film, the displaymedia comprising an electronic ink comprising an electrophoreticcontrast phase and a binder phase; and (c) printing a second electrodecovering at least a portion of the display media.
 2. The method of claim1, wherein step (b) comprises printing an encapsulated electrophoreticdisplay media on the first surface of the film, the display mediacomprising an encapsulated electrophoretic contrast phase and a binderphase.
 3. The method of claim 1, wherein step (c) comprises printing anopaque conducting electrode covering at least a portion of the displaymedia.
 4. The method of claim 3 wherein step (c) comprises printing asilver ink electrode covering at least a portion of the display media.5. The method of claim 3 wherein step (c) comprises printing a graphiteink electrode covering at least a portion of the display media.
 6. Themethod of claim 1 wherein step (a) comprises (a-a) providing a film; and(a-b) disposing an electrode structure on the film.
 7. The method ofclaim 6 wherein step (a-b) comprises printing an electrode structure onthe film.
 8. The method of claim 1 wherein step (a) comprises providinga polymer film having a substantially clear electrode structure disposedon a first surface of the film.
 9. The method of claim 8 wherein step(a) comprises providing a polyester film having a substantially clearelectrode structure disposed on a first surface of the film.
 10. Themethod of claim 1 wherein step (b) comprises printing a display media onthe first surface of the film, the display media comprising anencapsulated electrophoretic contrast phase and a binder phase, whereinthe material is encapsulated in capsules having an average diameter of100 microns.
 11. A method of printing a flexible, electrically activedisplay comprising the steps of: (a) providing a first film having anelectrode structure disposed on a first surface of the film; (b)printing an encapsulated electrophoretic contrast phase and a binderphase on the first surface of the first film; (c) providing a secondfilm; (d) printing an electrode structure on the second film; and (e)laminating the first film and the second film so that the printedelectrode structure is in electrical communication with the encapsulatedelectrophoretic contrast phase and the binder phase.
 12. The method ofclaim 11 wherein step (a) comprises: (a-a) providing a first film; and(a-b) disposing an electrode structure on the film.
 13. The method ofclaim 12 wherein step (a-b) comprises printing an electrode structure onthe film.
 14. The method of claim 11 wherein step (a) comprisesproviding a polymer film having an electrode structure disposed on afirst surface of the film.